Let's dive into this subtraction. We'll start with 68490 and subtract 24508 from it.

Step 1: We'll start by subtracting the digit 8 and the borrow 0 from 0 in column 1 and get -8.
We add -8 to 10 and get 2 as the first digit of the result.

Step 2: We'll start by subtracting the digit 0 and the borrow 1 from 9 in column 2 and get 8.
8 is the next digit of our result.

Step 3: We'll start by subtracting the digit 5 and the borrow 0 from 4 in column 3 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

Step 4: We'll start by subtracting the digit 4 and the borrow 1 from 8 in column 4 and get 3.
3 is the next digit of our result.

Step 5: We'll start by subtracting the digit 2 and the borrow 0 from 6 in column 5 and get 4.
4 is the next digit of our result.

So, 68490 - 24508 = 43982.